The glass sheets used as substrates for display applications, e.g., liquid crystal displays (LCDs) and organic light emitting diode (OLED) displays, need to have surfaces which are essentially free of defects having dimensions on the order of 1 micron and above. Accordingly, extensive efforts have been undertaken to find effective ways of inspecting glass sheets for such defects.
The small sizes of the defects, the fact that glass sheets are transparent at the wavelengths normally used for inspection, and the fact that the glass sheets are thin, e.g., on the order of 0.2 to 1.2 millimeters for display applications, has made inspection a challenging problem. Moreover, as demand for flat panel displays has increased, the number of glass making lines in operation has also increased. As a result, the need for inspection equipment has increased, thus making the cost and complexity of such equipment an important consideration in the evaluation of a system's suitability for this application.
As discussed below, the present disclosure provides inspection systems which can meet the performance criteria associated with the reliable inspection of display glass, while employing relatively inexpensive optical components that can be readily assembled into a compact device that can be easily deployed in a manufacturing setting.